Molecular dynamics simulations of ballistic He penetration into W fuzz

Show full item record



Permalink

http://hdl.handle.net/10138/308225

Citation

Klaver , T P C , Nordlund , K , Morgan , T W , Westerhof , E , Thijsse , B J & van de Sanden , M C M 2016 , ' Molecular dynamics simulations of ballistic He penetration into W fuzz ' , Nuclear Fusion , vol. 56 , no. 12 , 126015 . https://doi.org/10.1088/0029-5515/56/12/126015

Title: Molecular dynamics simulations of ballistic He penetration into W fuzz
Author: Klaver, T. P. C.; Nordlund, K.; Morgan, T. W.; Westerhof, E.; Thijsse, B. J.; van de Sanden, M. C. M.
Other contributor: University of Helsinki, Department of Physics
Date: 2016-12
Language: eng
Number of pages: 15
Belongs to series: Nuclear Fusion
ISSN: 0029-5515
DOI: https://doi.org/10.1088/0029-5515/56/12/126015
URI: http://hdl.handle.net/10138/308225
Abstract: Results are presented of large-scale Molecular Dynamics simulations of low-energy He bombardment of W nanorods, or so-called 'fuzz' structures. The goal of these simulations is to see if ballistic He penetration through W fuzz offers a more realistic scenario for how He moves through fuzz layers than He diffusion through fuzz nanorods. Instead of trying to grow a fuzz layer starting from a flat piece of bulk W, a new approach of creating a fully formed fuzz structure 0.43 mu m thick out of ellipsoidal pieces of W is employed. Lack of detailed experimental knowledge of the 3D structure of fuzz is dealt with by simulating He bombardment on five different structures of 15 vol% W and determining the variation in He penetration for each case. The results show that by far the most important factor determining He penetration is the amount of open channels through which He ions can travel unimpeded. For a more or less even W density distribution He penetration into fuzz falls off exponentially with distance and can thus be described by a 'half depth'. In a 15 vol% fuzz structure, the half depth can reach 0.18 mu m. In the far sparser fuzz structures that were recently reported, the half depth might be 1 mu m or more. This means that ballistic He penetration offers a more likely scenario than He diffusion through nanorods for how He moves through fuzz and may provide an adequate explanation for how He penetrates through the thickest fuzz layers reported so far. Furthermore, the exponential decrease in penetration with depth would follow a logarithmic dependence on fluence which is compatible with experiments. A comparison of these results and molecular dynamics calculations carried out in the recoil interaction approximation shows that results for W fuzz are qualitatively very different from conventional stopping power calculations on W with a similarly low but homogeneous density distribution.
Subject: W
fuzz
He bombardment
plasma
molecular dynamics
atomistic simulation
HELIUM PLASMA IRRADIATION
LOW-ENERGY
TUNGSTEN SURFACE
BUBBLE FORMATION
MECHANISM
GROWTH
RANGE
114 Physical sciences
Rights:


Files in this item

Total number of downloads: Loading...

Files Size Format View
Kla16preprint.pdf 10.30Mb PDF View/Open

This item appears in the following Collection(s)

Show full item record